Lithium batteries, including rechargeable or secondary lithium ion batteries, non-rechargeable or primary lithium batteries, and other types such as lithium-sulfur batteries, are typically made by interleaving a plastic separator, a conductive metal substrate with a cathode layer coated on both sides, another plastic separator, and another conductive metal substrate with an anode layer coated on both sides. To maintain the alignment of the strips of these materials and for other quality reasons, this interleaving is usually done on automatic equipment, which is complex and expensive. Also, in order to achieve sufficient mechanical strength and integrity, the separators and the metal substrates are relatively thick, such as 10 microns in thickness or more. For example, a typical thickness of the copper metal substrate for the anode coating layers is 10 microns, a typical thickness of the aluminum metal substrate for the cathode coating layers is 12 microns, and the plastic separators typically have thicknesses ranging from 12 to 20 microns. These thick separators and metal substrates are not electrochemically active and thus lower the volume of the electroactive material in the electrodes of the lithium batteries. This limits the energy density and power density of the lithium batteries.
Among the new applications for lithium batteries are high power batteries for hybrid, plug-in hybrid, and electric vehicles. In contrast to the cylindrical metal cells used in lithium batteries for portable computers and other applications, many of the lithium batteries for vehicles are of a flat or prismatic design. Also, the lithium batteries for vehicles need to be economical. Potential approaches to make higher energy and more economical lithium batteries for vehicles and other applications include greatly increasing the proportion or percentage of the volume of the electroactive material in each battery and reducing the complexity and expense of the automated equipment to fabricate the battery.
It would be advantageous if a lithium battery comprised separator and metal substrate layers that were much thinner than are currently used with either or both of its cathode and anode layers and thereby had a greater content of electroactive material. It would be particularly advantageous if this lithium battery could be fabricated on less complex and less expensive automated processing equipment than, for example, the winding equipment utilized for portable computer batteries, and furthermore was particularly adapted for making flat or prismatic batteries.